The present relates to a light amount control apparatus for controlling a light amount in projecting an image formed by image forming device of a liquid crystal panel or the like onto a screen with a projecting lens, and a projector apparatus using the same.
Generally, an apparatus for projecting a light image of a liquid crystal projector apparatus or the like onto a screen is widely used as an apparatus connected to an image apparatus of a computer, a television set, or the like for projecting an image outputted from the image apparatus onto a screen with a projecting lens.
A light image projected by such a projector apparatus is felt to be dazzling or dark depending on an environment where the apparatus is used. The reason is that, for example, in a state in which a pupil of a person using the apparatus at a dark place is opened, when a bright image is constituted abruptly, light is felt more strongly than actual light. Conversely, at a bright place, the screen is felt to be dark and therefore, an easiness to see depending on a surrounding brightness causes a problem. Further, there also causes a problem that even by an image viewed as in a flash image, an unpleasant feeling is felt by extremely stimulating a nerve of a person enjoying the image by changing the brightness of the image in an extremely short period of time though the nerve is stimulated temporarily.
It is necessary to control a brightness of an image projected to a screen in accordance with a surrounding environment or a viewing environment. In a related art, as a method of controlling the projected light amount, there is known a method of controlling a light source of irradiating light to a liquid crystal panel or the like, or controlling a voltage applied to the liquid crystal panel in, for example, Patent Reference 1 (Japanese Patent Publication (Kokai) No. 2000-28988)
In a related art, as a method of controlling the projected light amount (brightness of screen image), a method of controlling a voltage applied to a liquid crystal panel is known. However, a liquid crystal panel has a particular relationship between a voltage and a transmittance, and there poses a problem that in changing a brightness by changing the voltage, it is difficult to control the voltage such that red, blue, and green are uniformly changed, further, in controlling the brightness, also a tone of color is changed.
It is proposed in, for example, Patent Reference 2 (Japanese Patent Publication (Kokai) No. 2003-121938) to control a brightness of a screen image constant by controlling a light amount projected by a projecting lens by a light shielding mask plate. The reference discloses a constitution for providing a base member having a projecting hole (lens hole) in a direction orthogonal to a projecting light path of a projecting lens at a front face thereof and attaching a light shielding plate (mask member) for controlling an aperture of the projecting hole to be large or small at the base member opening and closing in the direction orthogonal to the light path to control a light amount. Therefore, by controlling an interval in irradiating an image formed at a liquid crystal panel onto a screen by a projecting lens by receiving light from a light source by controlling an opening of a light path to be large or small by a light shielding plate provided at a plane orthogonal to the projecting light path, a brightness of an image on the screen is controlled.
In controlling the light amount of the light path projected by the projecting lens as described above by the light shielding plate (mask member), when the light amount is intended to control by sliding to move the light shielding plate provided at the plane orthogonal to the projecting light path as disclosed in Patent Reference 2, a space for moving forward and rearward a light shielding member (mask plate in a blade-like shape or the like) and a space of arranging a drive mechanism for opening and closing the light shielding member are needed at a side portion of the projecting lens. The spaces become at least double of an area of the light shielding member. On the other hand, the projecting lens is normally constituted by a circular shape and integrated to a lens-barrel portion in a cylindrical shape. Accordingly, the light amount control apparatus is projected in a side direction of the lens. Therefore, an undesirable result for small-sized formation or space saving formation of the apparatus is brought about.
In order to resolve such a problem, the inventors have tried to achieve space saving formation and small-sized formation of an apparatus in comparison with those in the case of constituting the light shielding plate to be able to move forward and rearward in the plane orthogonal to the light path by providing a pair of light shielding plates (plate members) on the left and on the right of a light path of projecting onto a screen by a projecting lens and controlling an amount of opening the light path by pivoting the light shielding plates in a direction of advancing the light path.
However, there poses a problem that by adopting such a constitution, a center of a projecting light amount is shifted unless the pair of the shielding plates is moved to open and close by the same amount in synchronism with each other, and there poses a problem that depending on arrangement of a drive apparatus of a drive motor or the like relative to rotating shafts for supporting the light shielding plates, the apparatus is significantly projected in a side direction of the projecting light path similar to the related art. Accordingly, a mechanism in opening and closing the pair of light shielding plates by a drive apparatus of a motor or the like has a significant influence on a compactness of the apparatus.
In view of the problems described above, it is an object of the invention to provide a light amount control apparatus capable of achieving a small-sized compact formation of the apparatus by compactly arranging a mechanism for controlling a light amount of a projecting light path at a peripheral edge of the light path and firmly controlling the light amount and a projector apparatus using the same.
Further objects and advantages of the invention will be apparent from the following description of the invention.